This invention relates to a storage system, in particular, management of data whose preservation period is determined.
In a computer system comprising plural devices such as computers, it is required to establish synchronization of a time held by each device constituting the system. For instance, the time is used to create logs to be obtained in the computer system. With the logs, various situations, such as an influence exerted by an operation of a certain device on another device, are grasped.
In general, in order to establish time synchronization in the computer system, an NTP (Network Time Protocol) server is used. In other words, one of the devices in the computer system is set as the NTP server and transmits time information to each of the other devices, thereby allowing every device in the computer system to obtain the same time.
Meanwhile, among data stored in a storage system, there is data whose preservation for a certain period of time is obligated. Such data is, for instance, audit target data in a specific category of business.
There is a method with which a WORM (Write Once Read Many) attribute, in other words, an update prohibition attribute is given to such data at the time of storage, thereby proving that the data determined once is not erased or tampered and ensuring the correctness of the data.
In general, the WORM is a property possessed by write-once optical disks and the like (CD-Rs, for instance). Therefore, by storing data on such write-once media, the WORM attribute is realized with ease.
Aside from this, from the viewpoint of performance and the like, a method is also proposed with which the WORM is realized in a storage system comprising a magnetic disk.
In JP 07-13705 A, a method is disclosed with which overwriting of data on a disk is prevented by providing a writing prohibition flag or the like on the disk.